1. Gases

2. Temperature
Always use the Kelvin scale when working with gases. ºC K
-273
100
273
373
K = ºC + 273

3. Practice 23.5°C = __________K 296.5 K -15.4°C = _________ K 257.6 K

4. E. Pressure
Which shoes create the most pressure?

5. E. Pressure Barometer measures atmospheric pressure Aneroid Barometer
Mercury Barometer
Aneroid Barometer

6. E. Pressure KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm
760 mm Hg
760 torr
14.7 psi

7. Standard Temperature & Pressure
F. STP
STP
Standard Temperature & Pressure
0°C K
1 atm kPa
-OR-

8. Pressure Conversions Convert each of the following into mm Hg 1.25 atm
2.48 x 10-3 atm
4.75 x 104 atm

9. Answers
950. mm Hg
1.88 mm Hg
3.61 x 107 mm Hg

10. Pressure Conversions Convert 109 kPa to atm Convert 0.62 atm to mm Hg
Convert atm to kPa
Convert mmHg to kPa

11. Answers
1.08 atm
470 mm Hg
kPa
3.91 kPa

12. Gases
II. The Gas Laws P V T

13. Can you Explain the Following?
When deep sea fish rise through the water too quickly, their internal organs may be pushed out through their mouths.
Tire pressure decreases in colder weather
A balloon deflates in cold weather

14. Gas Law Animation

15. Boyle’s Law A. Pressure vs. Volume
The pressure and volume of a gas are inversely related
This means that when pressure increases, volume decreases and vice versa! P V

17. Charles’ Law B. Temperature vs. Volume
The volume and temperature (K) of a gas are directly related
When temperature increases, volume increases V T

19. Gay-Lussac’s Law C. Pressure vs. Temperature
The pressure and temperature (K) of a gas are directly related
When temp. increases, pressure increases P T

20. Combined Gas Law
P1V1 T1 =
P2V2 T2
P1V1T2 = P2V2T1

21. E. Gas Law Problems
A gas occupies 473 cm3 at 36°C. Find its volume at 94°C.
GIVEN:
V1 = 473 cm3
T1 = 36°C = 309K
V2 = ?
T2 = 94°C = 367K T V
WORK:
P1V1T2 = P2V2T1
(473 cm3)(367 K)=V2(309 K)
V2 = 562 cm3

22. E. Gas Law Problems
A gas occupies 100. mL at kPa. Find its volume at 200. kPa.
GIVEN:
V1 = 100. mL
P1 = 150. kPa
V2 = ?
P2 = 200. kPa P V
WORK:
P1V1T2 = P2V2T1
(150.kPa)(100.mL)=(200.kPa)V2
V2 = 75.0 mL

23. E. Gas Law Problems P T V V1 = 7.84 cm3 P1 = 71.8 kPa
A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find its volume at STP.
GIVEN:
V1 = 7.84 cm3
P1 = 71.8 kPa
T1 = 25°C = 298 K
V2 = ?
P2 = kPa
T2 = 273 K
P T V
WORK:
P1V1T2 = P2V2T1
(71.8 kPa)(7.84 cm3)(273 K)
=( kPa) V2 (298 K)
V2 = 5.09 cm3

24. E. Gas Law Problems
A gas’ pressure is 765 torr at 23°C. At what temperature will the pressure be 560. torr?
GIVEN:
P1 = 765 torr
T1 = 23°C = 296K
P2 = 560. torr
T2 = ? P T
WORK:
P1V1T2 = P2V2T1
(765 torr)T2 = (560. torr)(296K)
T2 = 217 K = -56°C